Method for manufacturing thin film transistor array substrate and thin film transistor array substrate for the same

ABSTRACT

A method for manufacturing a thin film transistor array substrate includes: forming a polysilicon layer on the substrate; forming a gate insulating layer on the polysilicon layer; forming a metal oxide layer on the gate insulating layer; forming a gate metal layer on the metal oxide layer; etching the metal oxide layer to define a gate; using the gate as a second mask and etching the metal oxide layer excluding a scope of the second mask; performing ion-implantation by using the gate and a remainder of the metal oxide layer as a third mask to form two lightly doped drain regions at opposite sides of the polysilicon layer; forming an insulating layer on the gate and the gate insulating layer respectively; forming a metal layer on the insulating layer and defining a drain and a source which connect to the doped drain region and the doped source region respectively.

FIELD OF THE INVENTION

The present invention relates to a method for manufacturing an arraysubstrate and a structure for the same, and more particularly, to amethod for manufacturing a low-temperature polysilicon thin filmtransistor array substrate and a structure of a low-temperaturepolysilicon thin film transistor array substrate.

BACKGROUND OF THE INVENTION

Liquid crystal displays having advantages over small size, light weight,and low power consumption are widely applied to various types ofelectronic products. In order to achieve high-precision components andpixel arrangement degrees, low-temperature polysilicon (LTPS) thin-filmtransistor liquid crystal displays have become the mainstream ofdevelopment.

However, low-temperature polysilicon has a problem that the conventionallow-temperature polysilicon thin film transistor (LTPS-TFT) structurecomprises two n-doped regions formed on a polysilicon layer as a sourceand a drain. Since a doping concentration of the two n-doped regions ishigher and a distance between the gate electrode and the n-doped regionis very small, a strong electric field closing to the drain causes a hotcarrier effect. Thus, a leakage current will occur while the polysiliconthin film transistor is in the OFF state. To solve this problem, theconventional technology uses a lightly doped drain (LDD) structure toreduce the electric field which is in contact with the drain and thusreduce the leakage current. Referring to FIG. 1, in the process ofmanufacturing a conventional low-temperature polysilicon thin filmtransistor, the formation of a self-aligned lightly doped drainstructure thin film transistor array substrate as below: 1. forming abuffer layer 11 and a non-polysilicon layer on a substrate 10, thenon-polysilicon layer crystallized into a polysilicon layer 12 by anexcimer laser annealing process, and defining a polysilicon region by amask; 2. defining a n-doped region by the mask and performing aion-implantation process to implant ions to form the n-doped region; 3.forming a gate insulating layer 14 on the polysilicon layer 12 by aplasma-enhanced chemical vapor deposition process; 4. forming a gate 15on the gate insulating layer 14, and defining a gate region by the mask,etching other metal by a dry etching process; 5. performing theion-implantation process (shown by the arrow in FIG. 1) and using thegate 15 as the mask to form a lightly doped drain region 16.

By etching the gate with the dry etching process, the gate insulatinglayer will also be etched and the gate insulating layer will be lost.While performing the ion-implantation process to form the lightly dopeddrain region, the ions implanted into the polysilicon layer will causethe dosage of the ions to be uneven. Thus, the electric properties ofeach where of the a channel of the thin-film transistor producesdifferences and results in the brightness of liquid crystal displaybeing uneven or dark spots may occasionally appear on the liquid crystaldisplay.

SUMMARY OF THE INVENTION

An objective of the present invention is to provide a method ofmanufacturing a thin film transistor array substrate and a structure ofa thin film transistor array substrate for preventing the loss of thegate insulating layer when performing the dry etching process on thegate. The present invention improves the ion dose uniformity of thethickness of the gate insulating layer, so that the ions implanted intothe lightly doped drain will remain consistent.

In order to achieve the aforementioned objective of the presentinvention, the present invention provides a method of manufacturing athin film transistor array substrate, comprising:

providing a substrate;

forming a polysilicon layer on the substrate;

forming a doped drain region and a doped source region in thepolysilicon layer;

forming a gate insulating layer on the polysilicon layer;

forming a metal oxide layer on the gate insulating layer;

forming a gate metal layer on the metal oxide layer;

etching the metal oxide layer by using a first mask to define a gate;

using the gate as a second mask and etching the metal oxide layerexcluding a scope of the second mask;

performing ion-implantation by using the gate and a remainder of themetal oxide layer as a third mask to form two lightly doped drainregions at the opposite sides of the polysilicon layer, the two lightlydoped drain region are in contact with the doped drain region and thedoped source region respectively;

forming an insulating layer on the gate and the gate insulating layerrespectively, and defining a via hole on the doped drain region and thedoped source region respectively;

forming a metal layer on the insulating layer and defining a drain and asource, the drain and the source being connected to the doped drainregion and the doped source region respectively through the via hole.

In the method described above, the method further comprises a step offorming a buffer layer on the substrate before forming the polysiliconlayer on the substrate.

In the method described above, a plurality of phosphorous ions areion-implanted into the polysilicon layer to form the doped drain regionand the doped source region.

In the method described above, the step of etching the gate metal layercomprises a dry etching process which is configured to etch the gatemetal layer excluding a scope of the first mask to form the gate, andthe step of etching the metal oxide layer comprises a wet etchingprocess which is configured to etch the metal oxide layer by using thegate as the second mask excluding the scope of the second mask.

In the method described above, the gate insulating layer is selectedfrom one of a silicon oxide layer, a silicon nitride layer, or a stackedlayer structure for both of the layers.

In the method described above, the metal oxide layer is made of IndiumTin Oxide.

In the method described above, a critical dimension bias between themetal oxide layer and the gate is less than 0.3 μm.

In the method described above, the method is for use in manufacturing anorganic light emitting diode display.

The present invention further provides a method of manufacturing a thinfilm transistor array substrate, comprising:

providing a substrate;

forming a polysilicon layer on the substrate;

forming a doped drain region and a doped source region in thepolysilicon layer;

forming a gate insulating layer on the polysilicon layer;

forming a metal oxide layer on the gate insulating layer;

forming a gate metal layer on the metal oxide layer;

etching the metal oxide layer by using a first mask to define a gate;

using the gate as a second mask and etching the metal oxide layerexcluding a scope of the second mask;

performing ion-implantation by using the gate and a remainder of themetal oxide layer as a third mask to form two lightly doped drainregions at the opposite sides of the polysilicon layer;

forming an insulating layer on the gate and the gate insulating layerrespectively, and defining a via hole on the doped drain region and thedoped source region respectively;

forming a metal layer on the insulating layer and defining a drain and asource, the drain and the source being connected to the doped drainregion and the doped source region respectively through the via hole.

In the method described above, the method further comprises a step offorming a buffer layer on the substrate before forming the polysiliconlayer on the substrate.

In the method described above, a plurality of phosphorous ions areion-implanted into the polysilicon layer to form the doped drain regionand the doped source region.

In the method described above, the step of etching the gate metal layercomprises a dry etching process which is configured to etch the gatemetal layer excluding a scope of the first mask to form the gate, andthe step of etching the metal oxide layer comprises a wet etchingprocess which is configured to etch the metal oxide layer by using thegate as the second mask excluding the scope of the second mask.

In the method described above, the gate insulating layer is selectedfrom one of a silicon oxide layer, a silicon nitride layer, or a stackedlayer structure for both of the layers.

In the method described above, the metal oxide layer is made of IndiumTin Oxide.

In the method described above, a critical dimension bias between themetal oxide layer and the gate is less than 0.3 μm.

In the method described above, the method is for use in manufacturing anorganic light emitting diode display.

The present invention further provides a thin film transistor arraysubstrate, comprising:

a substrate, a polysilicon layer formed on the substrate, a gateinsulating layer formed on the polysilicon layer, a gate formed on thegate insulating layer, the polysilicon layer having a doped drain regionand a doped source region and two lightly doped drain regions at theopposite sides of the polysilicon layer, an insulating layer formed onthe gate and the gate insulating layer respectively, a via hole formedon the doped drain region and the doped source region respectively, ametal layer formed on the insulating layer, the metal layer having adrain and a source, the drain and the source connected to the dopeddrain region and the doped source region respectively through the viahole;

wherein a metal oxide layer is formed between the gate and the gateinsulating layer, an overlying scope of the gate is the same as anoverlying scope of the metal oxide layer, the two lightly doped drainregions are not covered by the overlying scope of the gate and theoverlying scope of metal oxide layer.

In the substrate described above, a buffer layer is formed between thesubstrate and the polysilicon layer.

In the substrate described above, the metal oxide layer is made ofIndium Tin Oxide.

In the substrate described above, a critical dimension bias between themetal oxide layer and the gate is less than 0.3 μm.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view and process of the conventionallow-temperature polysilicon thin film transistor;

FIG. 2 is a flowchart of a method of manufacturing thin film transistorarray substrate according to a preferred embodiment of the presentinvention; and

FIG. 3-FIG. 9 illustrate schematic views and processes of the thin filmtransistor array substrate according to the preferred embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments adopted by the present invention are given inthe following detailed description, with reference to the drawings.

FIG. 2 is a flowchart of a method of manufacturing thin film transistorarray substrate according to a preferred embodiment of the presentinvention, which comprises; providing a substrate which is made oftransparent conductive material, such as glass, quartz, or the likewhich can be used for the substrate.

A polysilicon layer is formed on the substrate. Before forming thepolysilicon layer, a non-polysilicon layer formed on a substrate whichis crystallized into the polysilicon layer by an excimer laser annealingprocess to convert the non-polysilicon layer into the polysilicon layeras a channel region of the thin-film transistor. A polysilicon region(not shown) is defined by a masking and an etching process. In otherembodiment of the present invention, the method further comprises a stepof forming a buffer layer on the substrate before forming thepolysilicon layer on the substrate.

The polysilicon layer is to apply a photoresist onto and apply a backsurface light exposure process to the substrate for defining aphotoresist pattern on the polysilicon layer, then performing anion-implantation by using the photoresist pattern as a mask to form adoped drain region and a doped source region in the polysilicon layer.In an n-type thin film transistor, the ion-implantation uses ionsselected from pentavalent ions, such as phosphorus ion or arsenic ion.In a p-type thin film transistor, the ion-implantation uses ionsselected from trivalent ions, such as boron ion and gallium ion. In thisembodiment of the present invention, phosphorus ion implanted in thepolysilicon region of the polysilicon layer to form the doped drainregion and the doped source region which are formed at the oppositesides of the polysilicon layer respectively.

A gate insulating layer is formed on the polysilicon layer by performinga plasma-enhanced chemical vapor deposition process. In this embodimentof the present invention, the gate insulating layer is selected from oneof a silicon oxide layer, a silicon nitride layer, or a stacked layerstructure for both of the layers, but not limited thereto.

A metal oxide layer is formed on the gate insulating layer. Preferably,the metal oxide layer is made of Indium Tin Oxide, but is not limitedthereto.

A gate metal layer is formed on the metal oxide layer. Using a firstmask to define a gate region (not shown), and performing an etchingprocess toward the metal oxide layer to define a gate. In thisembodiment of the present invention, the step of etching the gate metallayer comprises a dry etching process which is configured to etch thegate metal layer excluding a scope of the first mask to form the gate.The reason for performing the dry etching process is mainly due to thenumber of pulses per inch (ppi) being high, a critical dimension bias inthe dry etching process will be smaller than the critical dimension biasin a wet etching process.

Then, the gate is used as a second mask and the metal oxide layer isetched excluding a scope of the second mask. In this embodiment of thepresent invention, the step of etching the metal oxide layer comprises awet etching process which is configured to etch the metal oxide layer byusing the gate as the second mask excluding the scope of the secondmask.

Then, ion-implantation is performed by using the gate and a remainder ofthe metal oxide layer as a third mask to form two lightly doped drainregions at opposite sides of the polysilicon layer. The remainder of themetal oxide layer is formed between the gate and the gate insulatinglayer. Furthermore, an overlying scope of the gate is the same as anoverlying scope of the remainder of the metal oxide layer. Namely, theion-implantation uses the gate and a remainder of the metal oxide layeras the third mask. Thus, the overlying scope of the gate and theoverlying scope of the remainder of the metal oxide layer do not coverwith the lightly doped drain regions. The lightly doped drain regionsare out of the overlying scope of the gate and the overlying scope ofthe remainder of the metal oxide layer. The two lightly doped drainregions are in contact with the doped drain region and the doped sourceregion respectively so as to achieve the effect of self-aligning andfurther to control a shift (critical dimension bias) between the gateand the remainder of the metal oxide layer, as the third mask is lessthan 0.3 μm for preventing the critical dimension bias and not doesaffect a width of the gate.

The follow steps form an insulating layer on the gate and the gateinsulating layer respectively, forming a metal layer on the insulatinglayer and defining a drain and a source, and forming a via hole by usinga mask in the insulating layer corresponding to the drain and the sourcerespectively. The doped drain region and the doped source region of thepolysilicon layer correspond to the via hole respectively. The drain andthe source connect to the doped drain region and the doped source regionrespectively through the via hole.

In addition, referring to FIG. 3-FIG. 9, the present invention providesa thin film transistor array substrate, which comprises: a substrate 20,a polysilicon layer 22 formed on the substrate 20, a gate insulatinglayer 23 formed on the polysilicon layer 22, a gate 24 formed on thegate insulating layer 23, the polysilicon layer 22 having a doped drainregion 221 and a doped source region 222 and two lightly doped drainregions 30 at the opposite sides of the polysilicon layer 22, aninsulating layer 25 formed on the gate 24 and the gate insulating layer23 respectively, a via hole 27 formed in the insulating layer 25 andcorresponding to the doped drain region 221 and the doped source region222 respectively, a metal layer 28 formed on the insulating layer 25,the metal layer 28 having a drain 281 and a source 282, the drain 281and the source 282 connect to the doped drain region 221 and the dopedsource region 222 respectively through the via hole 27.

A metal oxide layer 26 is formed between the gate 24 and the gateinsulating layer 23, an overlying scope of the gate 24 is the same as anoverlying scope of the metal oxide layer 26, the two lightly doped drainregions 30 are not covered by the overlying scope of the gate 24 and theoverlying scope of metal oxide layer 26.

Preferably, in this embodiment of the present invention, the thin filmtransistor array substrate uses the gate 24 and the metal oxide layer 26as the mask to perform the ion-implantation toward the lightly dopeddrain regions 30 (shown by the arrow of FIG. 7). Referring to FIG. 7 andobserving from a vertical direction, the gate 24, the metal oxide layer26 and the lightly doped drain regions 30 are aligned with each other.The overlying scope of the gate 24 and the overlying scope of the metaloxide layer 26 do not cover with the lightly doped drain regions 30.

Preferably, the metal oxide layer 26 is made of Indium Tin Oxide. Acritical dimension bias between the metal oxide layer 26 and the gate 24is less than 0.3 μm. The thin film transistor array substrate is for usein manufacturing an organic light emitting diode display.

In another embodiment of the present invention, a buffer layer formedbetween the substrate and the polysilicon layer.

As described above, the present invention provides a method ofmanufacturing a thin film transistor array substrate and a thin filmtransistor array substrate. The metal oxide layer is disposed under thegate so that the metal oxide layer resists the etching to the gateinsulating layer when the gate performs the dry etching process. Thiscan improve the uniformity of the gate insulating layer, and thecritical dimension bias between the gate and the metal oxide layer isless than 0.3 μm for preventing the loss of the gate insulating layerwhen performing the dry etching process to the gate. The presentinvention also can provide better uniformity of the ion-implantation ofthe lightly doped drain regions in depth and dosage and ensure that theion dosage implanted into the lightly doped drain regions remainconsistent. Thus, the present invention prevents the ion dosageimplanted into the lightly doped drain regions from being uneven andcauses the electric property of each where of the a channel of thethin-film transistor produces differences and resulting in thebrightness of liquid crystal display being uneven or dark spots mayoccasionally appear on the liquid crystal display.

Although the present invention has been described with the preferredembodiments thereof, those skilled in the art will appreciate thatvarious modifications, additions, and substitutions are possible,without departing from the scope and the spirit of the invention.Accordingly, the scope of the present invention is intended to bedefined only by reference to the claims.

What is claimed is:
 1. A method for manufacturing a thin film transistorarray substrate, comprising: providing a substrate; forming apolysilicon layer on the substrate; forming a doped drain region and adoped source region in the polysilicon layer; forming a gate insulatinglayer on the polysilicon layer; forming a metal oxide layer on the gateinsulating layer; forming a gate metal layer on the metal oxide layer;etching the metal oxide layer by using a first mask to define a gate;using the gate as a second mask and etching the metal oxide layerexcluding a scope of the second mask; performing ion-implantation byusing the gate and a remainder of the metal oxide layer as a third maskto form two lightly doped drain regions at opposite sides of thepolysilicon layer, the two lightly doped drain region being in contactwith the doped drain region and the doped source region respectively;forming an insulating layer on the gate and the gate insulating layerrespectively, and defining a via hole on the doped drain region and thedoped source region respectively; forming a metal layer on theinsulating layer and defining a drain and a source, the drain and thesource being connected to the doped drain region and the doped sourceregion respectively through the via hole.
 2. The method according toclaim 1, further comprising a step of forming a buffer layer on thesubstrate before forming the polysilicon layer on the substrate,
 3. Themethod according to claim 1, wherein a plurality of phosphorous ions areion-implanted into the polysilicon layer to form the doped drain regionand the doped source region.
 4. The method according to claim 1, whereinthe step of etching the gate metal layer comprises a dry etching processwhich is configured to etch the gate metal layer excluding a scope ofthe first mask to form the gate, and the step of etching the metal oxidelayer comprises a wet etching process which is configured to etch themetal oxide layer by using the gate as the second mask excluding thescope of the second mask.
 5. The method according to claim 1, whereinthe gate insulating layer is selected from one of a silicon oxide layer,a silicon nitride layer, or a stacked layer structure for both of thelayers.
 6. The method according to claim 1, wherein the metal oxidelayer is made of Indium Tin Oxide.
 7. The method according to claim 1,wherein a critical dimension bias between the metal oxide layer and thegate is less than 0.3 μm.
 8. The method according to claim 1 being foruse in manufacturing an organic light emitting diode display.
 9. Amethod for manufacturing a thin film transistor array substrate,comprising: providing a substrate; forming a polysilicon layer on thesubstrate; forming a doped drain region and a doped source region in thepolysilicon layer; forming a gate insulating layer on the polysiliconlayer; forming a metal oxide layer on the gate insulating layer; forminga gate metal layer on the metal oxide layer; etching the metal oxidelayer by using a first mask to define a gate; using the gate as a secondmask and etching the metal oxide layer excluding a scope of the secondmask; performing ion-implantation by using the gate and a remainder ofthe metal oxide layer as a third mask to form two lightly doped drainregions at the opposite sides of the polysilicon layer; forming aninsulating layer on the gate and the gate insulating layer respectively,and defining a via hole on the doped drain region and the doped sourceregion respectively; forming a metal layer on the insulating layer anddefining a drain and a source, the drain and the source being connectedto the doped drain region and the doped source region respectivelythrough the via hole.
 10. The method according to claim 9 furthercomprising a step of forming a buffer layer on the substrate beforeforming the polysilicon layer on the substrate.
 11. The method accordingto claim 9, wherein a plurality of phosphorous ions are ion-implantedinto the polysilicon layer to form the doped drain region and the dopedsource region.
 12. The method according to claim 9, wherein the step ofetching the gate metal layer comprises a dry etching process which isconfigured to etch the gate metal layer excluding a scope of the firstmask to form the gate, and the step of etching the metal oxide layercomprising a wet etching process which is configured to etch the metaloxide layer by using the gate as the second mask excluding the scope ofthe second mask.
 13. The method according to claim 9, wherein the gateinsulating layer is selected from one of a silicon oxide layer, asilicon nitride layer, or a stacked layer structure for both of thelayers.
 14. The method according to claim 9, wherein the metal oxidelayer is made of Indium Tin Oxide.
 15. The method according to claim 9,wherein a critical dimension bias between the metal oxide layer and thegate is less than 0.3 μm.
 16. The method according to claim 9 being foruse in manufacturing an organic light emitting diode display.
 17. A thinfilm transistor array substrate, comprising: a substrate, a polysiliconlayer formed on the substrate, a gate insulating layer formed on thepolysilicon layer, a gate formed on the gate insulating layer, thepolysilicon layer having a doped drain region and a doped source regionand two lightly doped drain regions at opposite sides of the polysiliconlayer, an insulating layer formed on the gate and the gate insulatinglayer respectively, a via hole formed on the doped drain region and thedoped source region respectively, a metal layer formed on the insulatinglayer, the metal layer having a drain and a source, the drain and thesource connected to the doped drain region and the doped source regionrespectively through the via hole; wherein a metal oxide layer is formedbetween the gate and the gate insulating layer, an overlying scope ofthe gate is the same as an overlying scope of the metal oxide layer, thetwo lightly doped drain regions are not covered by the overlying scopeof the gate and the overlying scope of metal oxide layer.
 18. The thinfilm transistor array substrate according to claim 17, furthercomprising a buffer layer formed between the substrate and thepolysilicon layer.
 19. The thin film transistor array substrateaccording to claim 17, wherein the metal oxide layer is made of IndiumTin Oxide.
 20. The thin film transistor array substrate according toclaim 17, wherein a critical dimension bias between the metal oxidelayer and the gate is less than 0.3 μm.